President Wooddrow Wilson plans was not to spend much time in foreign affairs and keep his neutrality so America cannot be seen as peace breakers.
Nevertheless the sinking of the passenger liner Lusitania by a German U-Boat changed his mind. He asked for an apology from Germany and stayed neutral as long as possible, till president Wilson finally asked Congress for a formal declaration of war after the intention of Germany to give US territory to Mexico in return for supporting the German cause.